1. Field of the Invention
This invention relates to semiconductor integrated circuits, and more particularly, to the packaging and efficient cooling of multi-chip modules comprising a multi-layer ceramic substrate on which are mounted and interconnected an assemblage of semiconductor chips.
2. Background Information
In order to place the present invention in proper context and to provide a complete background for understanding its important features and advantages, reference may be made to an article in the IBM Journal of Research and Development, Volume 26, No. 1 of January 1982 by Blodgett and Barbour. There is described in that article, which is incorporated herein by reference, a recently developed thermal conduction module (TCM) which, in essence, involves a multi-layer ceramic package which provides for efficient cooling of a large number of integrated circuits embedded in semiconductor chips which are suitably interconnected and form part of said module.
The described thermal conduction module represents a breakthrough in high-performance package design and concept. Its significance lies in its ability to provide large scale integration (LSI) capability in the so called first level package, thereby allowing the advantages in cost, performance, and reliability already achieved at the chip level to be realized at the package level. It is extremely important to be able to produce large, complex, tight tolerance, multi-layer ceramic structures so as to provide the required LSI interconnection capability, high performance wiring and power distribution. However, the crucial factor in achieving these objectives is a cooling scheme which can overcome the thermal limitation which has so far stood in the way of high performance LSI at the package level. To understand the heat dissipation requirements, which are approximately 300 watts, it must be appreciated that a typical thermal conduction module, as described in the cited article, includes 100 chips containing 25,000 logic circuits and 65,000 bits of storage. Furthermore, the module is provided with 1800 pins to interface with a second level package.
A further critical aspect of the thermal conduction module design and construction is the ability to re-work the assembly so as to be able to make engineering changes. Thus, it must be possible to break the helium seal so that individual chips can be replaced and wires can be deleted. Such a feature is essential during the design and de-bug phase of system development.